Gasification reactor with discrete reactor vessel and grate and method of gasification

Abstract

A fluidized bed biogasifier is provided for gasifying biosolids. The biogasifier includes a reactor vessel and a feeder for feeding biosolids into the reactor vessel at a desired feed rate during steady-state operation of the biogasifier. A fluidized bed in the base of the reactor vessel has a cross-sectional area that is proportional to at least the fuel feed rate such that the superficial velocity of gas is in the range of 0.1 m/s (0.33 ft/s) to 3 m/s (9.84 ft/s). In a method for gasifying biosolids, biosolids are fed into a fluidized bed reactor. Oxidant gases are applied to the fluidized bed reactor to produce a superficial velocity of producer gas in the range of 0.1 m/s (0.33 ft/s) to 3 m/s (9.84 ft/s). The biosolids are heated inside the fluidized bed reactor to a temperature range between 900° F. (482.2° C.) and 1700° F. (926.7° C.) in an oxygen-starved environment having a sub-stoichiometric oxygen level, whereby the biosolids are gasified.

What is claimed is: 
     
       1. A gasification reactor comprising:
 a discrete reactor vessel which is cylindrical in shape having a bottom with an inverted cone section; 
 a freeboard section comprising the top half of the reactor vessel, said freeboard section having a diameter of at least 57 inches; 
 a fluidized bed in a bed section within said reactor vessel located beneath the freeboard section, said fluidized bed having a diameter of at least 45 inches; 
 at least one fuel feed inlet located beneath the freeboard section, said inlet configured to feed a fuel into said reactor vessel at a fuel feed rate during steady-state operation of the gasifier; 
 a gas distributor located within the inverted cone section comprising a flue gas and air inlet that feeds flue gas and air to an array of nozzles whereby the flue gas and air are directed into the fluidized bed in the bed section; and 
 an ash grate positioned beneath the bottom of the discrete reactor vessel. 
 
     
     
       2. The reactor of  claim 1 , further comprising at least one inlet for a natural gas and air mixture. 
     
     
       3. The reactor of  claim 1 , further comprising at least one inlet for addition of an inert media. 
     
     
       4. The reactor of  claim 1 , further comprising an outlet for agglomerates; and an outlet for producer gas. 
     
     
       5. The reactor of  claim 1 , wherein the freeboard section is configured to provide particle entrainment out of the reactor. 
     
     
       6. The reactor of  claim 1 , wherein the freeboard section has a diameter greater than the fluidized bed such that a superficial velocity range of gas inside the freeboard section during steady state operation is between 0.1 m/s (0.33 ft/s) and 3 m/s (9.84 ft/s). 
     
     
       7. A method of gasification comprising:
 Supplying fuel through at least one inlet into a gasification reactor; 
 Introducing a fluidizing agent through at least one inlet into the gasification reactor; 
 Distributing the fluidizing agent within the reactor; and 
 Producing the outflow of producer gas through a top portion of the gasification reactor, 
 Said gasification reactor comprising:
 a discrete reactor vessel which is cylindrical in shape having a bottom with an inverted cone section; 
 a freeboard section comprising the top half of the reactor vessel, said freeboard section having a diameter of at least 57 inches; 
 a fluidized bed in a bed section within said reactor vessel located beneath the freeboard section, said fluidized bed having a diameter of at least 45 inches; 
 at least one fuel feed inlet located beneath the freeboard section, said inlet configured to feed a fuel into said reactor vessel at a fuel feed rate during steady-state operation of the gasifier; 
 a gas distributor located within the inverted cone section comprising a flue gas and air inlet that feeds flue gas and air to an array of nozzles whereby the flue gas and air are directed into the fluidized bed in the bed section; and 
 an ash grate positioned beneath the bottom of the discrete reactor vessel. 
 
 
     
     
       8. The method of  claim 7 , wherein the thermochemical conversion process occurs with an oxygen-to-fuel equivalence ratio between 0.1 and 0.5. 
     
     
       9. The method of  claim 7 , wherein a superficial velocity of producer gas inside the freeboard section during steady state operation is between 0.1 m/s (0.33 ft/s) and 3 m/s (9.84 ft/s). 
     
     
       10. The method of  claim 7 , wherein a thermochemical conversion process occurs within the reactor at a temperature between 900° F. (482.2° C.) and 1700° F. (926.7° C.). 
     
     
       11. The method of  claim 7 , further comprising the step of using a cyclone separator to separate material exhausted from said reactor into producer gas and ash.